Extreme ultraviolet light source apparatus

ABSTRACT

An extreme ultraviolet light source apparatus has a magnetic field generator which generates a magnetic field region around a direction of the magnetic field passing through a plasma region in which a plasma is to be generated and converges charged particles including ion emitted from the plasma region toward the direction of the magnetic field, a first charged particle collector (receiver) mounted at both sides of an axis of the magnetic field in the magnetic field region in order to collect (receive) the charged particles converged by the magnetic field, a target supply unit supplying a target from a nozzle located outside a converging region in which the charged particles are to be converged inside the magnetic field region in an extreme ultraviolet light generating chamber, and a target collector located at a position opposite to the nozzle, the target retrieval portion retrieving a residual target which does not contribute to generation of the plasma.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2008-273504, filed on Oct.23, 2008, and No. 2009-242868, filed on Oct. 21, 2009; the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an extreme ultraviolet light sourceapparatus outputting an extreme ultraviolet light emitted from plasmagenerated by irradiating a target with a laser light.

2. Description of the Related Art

In recent years, along with a progress in miniaturization ofsemiconductor device, miniaturization of transcription pattern used inphotolithography in a semiconductor process has developed rapidly. Inthe next generation, microfabrication to the extent of 70 nm to 45 nm,or even to the extent of 32 nm and beyond will be required. Therefore,in order to comply with the demand of microfabrication to the extent of32 nm and beyond, development of such on exposure apparatus combining anextreme ultraviolet (EUV) light source for a wavelength of about 13 nmand a reflection-type reduction projection optical system is expected.

As the EUV light source, there are three possible types, which are alaser produced plasma (LPP) light source using plasma generated byirradiating a target with a laser beam, a discharge produced plasma(DPP) light source using plasma generated by electrical discharge, and asynchrotron radiation (SR) light source using orbital radiant light.Among these light sources, the LPP light source has the advantage ofobtaining extremely high optical intensity close to the black-bodyradiation because plasma density can be made higher than the DPP lightsource and the SR light source. Moreover, the LPP light source has theadvantage of obtaining a strong light with a desired wavelength band byselecting a target material. Furthermore, the LPP light source is apoint light source which has no electrode located around a luminouspoint and has a nearly isotropic angular distributions. Therefore,extremely wide collecting solid angle can be acquired. The LPP lightsource with the above-mentioned advantages has attracted attention as alight source for EUV lithography which requires more than several dozento several hundred watt power.

In the EUV light source apparatus with the LPP system, firstly, a targetmaterial supplied inside a vacuum chamber is irradiated with a laserlight to be ionized and thus generate plasma. Then, a cocktail lightwith various wavelength components including an EUV light is emittedfrom the generated plasma. The EUV light source apparatus collects theEUV light by reflecting the EUV light using an EUV collector mirrorwhich selectively reflects the EUV light with a desired wavelengthcomponent, such as a 13.5 nm wavelength component, for instance. Thecollected EUV light enters an exposure apparatus. On a reflectivesurface of the EUV collector mirror, a multilayer coating, with astructure in that thin coatings of molybdenum (Mo) and thin coatings ofsilicon (Si) are alternately stacked, for instance, is formed. Themultilayer coating has a high reflectance ratio (of about 60% to 70%)for the EUV light with a 13.5 nm wavelength.

Here, as mentioned above, plasma is generated by irradiating a targetwith a laser light, and at the same time, particles (debris) such asgaseous ion particles and neutral particles, and tiny particles (metalcluster) which have not been able to become plasma fly out aroundthereof from a plasma luminescence point. The debris fly toward surfacesof various optical elements such as an EUV collector mirror located inthe vacuum chamber, focusing mirrors for focusing a laser light on atarget, and other optical system for measuring an EUV light intensity,and so forth. Therefore, fast ion debris with comparatively high energyerode surfaces of optical elements and damage reflective coating of thesurfaces. As a result, the surfaces of the optical elements will becomea metal component, which is a target material. On the other hand, slowion debris with comparatively low energy and neutral particle debriswill deposit on surfaces of optical elements. As a result, a layer of acompound of metal, which is a target material, is formed on the surfacesof the optical elements. As a result of the debris entering as mentionedabove, the reflective coating of each optical element is damaged or acompound layer is formed on the surfaces of the optical elements,whereby reflectance or transmittance of the optical elements decreaseand the optical elements become unusable.

In this respect, Japanese patent application Laid-Open No. 2005-197456discloses a technique such that debris flying from plasma are trapped bya magnetic field generated inside an optical collecting system by amagnetic field generator when current is supplied to the magnetic fieldgenerator. According to this technique, by locating a luminescence pointof an EUV light within the magnetic field, ion debris flying from theplasma generated around the luminescence point converge in a directionof the magnetic field by Lorentz force by the magnetic field. As aresult, contamination of neighboring optical elements with debris anddamages of the optical elements can be reduced.

However, in the above-mentioned Japanese Patent Application Laid-OpenNo. 2005-197456, because a target nozzle is located on the same axiswith a magnetic field direction, fast ion debris moving along themagnetic field collide with the target nozzle. As a result, the targetnozzle head will be sputtered by ion collision, whereby a shape of thenozzle head will change. Change of the shape of the nozzle head degradesa position stability of a droplet in a case, for instance, where thetarget is supplied to the plasma luminescence point as the droplet.Furthermore, the nozzle being sputtered induces another factor ofcontamination of optical elements such as materials of the nozzlereleased by the sputtering adhering to the optical elements.

As a technique to solve the above-mentioned problems, for example,Japanese Patent Application Laid-Open No. 2007-207574 discloses astructure with which collision of debris against a nozzle and opticalelements located in a direction for supplying droplet is reduced byarranging the nozzle in a direction perpendicular to a magnetic fielddirection.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, an extremeultraviolet light source apparatus generating an extreme ultravioletlight from plasma generated by irradiating a target with a laser light,the extreme ultraviolet light source apparatus comprises: a magneticfield generator which generates a magnetic field region around adirection of the magnetic field passing through a plasma region in whichthe plasma is to be generated and converges charged particles includingion emitted from the plasma region toward the direction of the magneticfield; a first charged particle collector (receiver) mounted at bothsides of an axis of the magnetic field in the magnetic field region inorder to collect (receive) the charged particles converged by themagnetic field; a target supply unit supplying a target from a nozzlelocated outside a converging region in which the charged particles areto be converged inside the magnetic field region in an extremeultraviolet light generating chamber; and a target collector located ata position opposite to the nozzle, the target collector collecting aresidual target which does not contribute to generation of the plasma.

These and other objects, features, aspects, and advantages of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which, taken in conjunction with theannexed drawings, discloses preferred embodiments of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of an extreme ultravioletlight source apparatus according to a first embodiment of the presentinvention when the extreme ultraviolet light source apparatus is cut ata cross-sectional face perpendicular to an optical axis of an EUV light;

FIG. 2 is a vertical cross-sectional view of the extreme ultravioletlight source apparatus according to the first embodiment when theextreme ultraviolet light source apparatus is cut at a face includingthe optical axis of the EUV light;

FIG. 3 is a schematic view showing a state around a plasma luminescencepoint;

FIG. 4 is a schematic view for explaining a tilt angle of a nozzle;

FIG. 5 is a schematic view for explaining a relationship among thenozzle, a converging portion and a collection cylinder;

FIG. 6 is a schematic view for explaining Larmar radius;

FIG. 7 is a schematic view showing a movement of a droplet inside amagnetic field;

FIG. 8 is a schematic view for explaining a movement of an emitteddroplet inside the magnetic field;

FIG. 9 is a schematic view for explaining a movement of a droplet in themagnetic field;

FIG. 10 is a vertical cross-sectional view of an extreme ultravioletlight source apparatus according to a second embodiment of the presentinvention when the extreme ultraviolet light source apparatus is cut ata cross-sectional face perpendicular to an optical axis of an EUV light;

FIG. 11 is a cross-sectional view showing a structure around a nozzlehead in an extreme ultraviolet light source apparatus according to athird embodiment of the present invention;

FIG. 12 is a schematic view showing a structure around the nozzle headin the extreme ultraviolet light source apparatus according to the thirdembodiment;

FIG. 13A is a lateral view showing a structure around a nozzle head inan extreme ultraviolet light source apparatus according to a firstalternate example of the third embodiment;

FIG. 13B is a cross-sectional view showing a structure around the nozzlehead in the extreme ultraviolet light source apparatus according to thefirst alternate example of the third embodiment;

FIG. 14 is a vertical cross-sectional view showing a structure around anozzle head in an extreme ultraviolet light source apparatus accordingto a second alternate example of the third embodiment;

FIG. 15A is a lateral view showing a structure around the nozzle head inthe extreme ultraviolet light source apparatus according to the secondalternate example of the third embodiment;

FIG. 15B is a horizontal cross-sectional view showing a structure aroundthe nozzle head in the extreme ultraviolet light source apparatusaccording to the second alternate example of the third embodiment;

FIG. 16 is a vertical cross-sectional view of an extreme ultravioletlight source apparatus according to a fourth embodiment of the presentinvention when the extreme ultraviolet light source apparatus is cut ata face including an optical axis of an EUV light;

FIG. 17 is an illustration showing an example of a far field patterntranscribed on A-A surface in FIG. 16;

FIG. 18 is a vertical cross-sectional view of an extreme ultravioletlight source apparatus according to a fifth embodiment of the presentinvention when the extreme ultraviolet light source apparatus is cut ata face including an optical axis of an EUV light; and

FIG. 19 is an illustration showing an example of a far field patterntranscribed on B-B surface in FIG. 18.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of an extreme ultraviolet light source apparatusaccording to the present invention will be described below in detailwith reference to the accompanying drawings.

First Embodiment

FIG. 1 is a vertical cross-sectional view of an extreme ultravioletlight source apparatus according to a first embodiment of the presentinvention when the extreme ultraviolet light source apparatus is cut ata cross-sectional face perpendicular to an optical axis of an EUV light.FIG. 2 is a vertical cross-sectional view of the extreme ultravioletlight source apparatus according to the first embodiment when theextreme ultraviolet light source apparatus is cut at a face includingthe optical axis of the EUV light. FIG. 3 is a schematic view showing astate around a plasma luminescence point. In FIGS. 1 to 3, the extremeultraviolet light source apparatus has a vacuum chamber 1 where a plasmaluminescence point P1 is located at a central position of the vacuumchamber 1. A CO₂ pulse laser light La emitted from a drive laser 2located outside the vacuum chamber 1 is inputted inside the vacuumchamber 1 through a window 1 a for inputting a laser light in the vacuumchamber 1. The CO₂ pulse laser light La is focused on the plasmaluminescence point P1 via a light focusing optical system 3 and anaperture 8 a of an EUV collector mirror 8 in the vacuum chamber 1.

Furthermore, a Sn tank 5 mounted outside the vacuum chamber 1 stores amolten metal of Sn, and ejects a droplet 17 of Sn, which is a target,from a nozzle 7 through a supply tube 6. The nozzle 7 ejects the droplet17 so that the droplet 17 passes through the plasma luminescence pointP1. Here, an ejection timing and a pulse timing of the CO₂ pulse laserlight La for each droplet 17 are controlled to be synchronous by acontroller (not shown) so that each droplet 17 is irradiated with theCO₂ pulse laser light La at the plasma luminescence point P1. A laserdumper 18 is arranged for absorbing the laser light from the drive laser2.

In the vacuum chamber 1, the EUV collector mirror 8 is arranged. The EUVcollector mirror 8 reflects an EUV light Lb emitted from a plasmagenerated by irradiating the droplet with the CO₂ pulse laser light Laso that the EUV light Lb is focused. The reflected EUV light Lb isoutputted to an exposure apparatus (not shown) via a vacuum valve 1 b.Here, a spectrum filter transmitting only an EUV light with a desiredwavelength can be arranged in place of the vacuum valve 1 b. A specificexample of the spectrum filter can be a thin film filter of Zr, or thelike.

Here, in the vacuum chamber 1, a pair of magnets 11 a and 11 bsandwiching the plasma luminescence point P1 in between are arranged.The magnets 11 a and 11 b generate a magnetic field of which an axisdirection passes through the plasma luminescence point P1 forcontrolling a moving direction of charged particles including ionsgenerated at the plasma luminescence point P1. In this case, the magnetis a superconducting magnet or a magnet coil. The charged particles(also referred to as ion debris) such as Sn⁺ ion, electron, and soforth, diffusing from Sn plasma converge within a certain range lyingalong a magnetic direction based on a valence and energy of the chargedparticles and a magnetic flux density at a location of the chargedparticles.

The charged particles converged within a convergence region E2 arecollected (received) by charged particle collection (receiving)cylinders 12 a and 12 b mounted at both edges of a direction of appliedmagnetic field passing through the plasma luminescence point P1.Furthermore, droplets which did not contribute to generation of the EUVlight Lb although being ejected from the nozzle are collected by targetcollection cylinders 14 located at positions facing to each other whilesandwiching the plasma luminescence point P1 in between.

Here, in this particular embodiment, the droplet which did notcontribute to generation of the EUV light Lb means a dropletcorresponding to either one of the following two droplets. The first oneis a droplet irradiated with a laser light however the target materialdid not contribute to an EUV luminescence (a deformed droplet, ascattered tiny particle). The second one is a droplet which was notirradiated with a laser light. In addition, the second droplet is adroplet in a case where a track of the droplet (track C1 of droplet: cf.FIG. 3) does not pass through an irradiation position of a laser light(the plasma luminescence point P1) or a case where the droplet (targetmaterial) is not irradiated with a laser light even if the dropletpasses through the irradiation position.

The charged particle collection (receiving) cylinders 12 a and 12 b andthe target collection cylinder 14 can have drain tubes 13 a, 13 b and 15for ejecting the collected Sn outside of the vacuum chamber 1. Thecollected Sn can be melted in order to be ejected easily. In this case,the drained Sn can be supplied to the Sn tank 5 again after a recycleprocess.

The nozzle 7, the supply tube 6, the charged particle collection(receiving) cylinders 12 a and 12 b, the target collection cylinder 14and the drain tubes 13 a, 13 b and 15 are located inside a space betweenthe EUV collector mirror 8 and the magnets 11 a and 11 b, for instance.However, it is not limited to the above arrangement, while the nozzle 7,the supply tube 6, the charged particle collection (receiving) cylinders12 a and 12 b, the target collection cylinder 14 and the drain tubes 13a, 13 b and 15 can be located in such a way as not to prevent generationand collection of the EUV light Lb. In this arrangement, it ispreferable that the nozzle 7, the supply tube 6, the charged particlecollection (receiving) cylinders 12 a and 12 b, the target collectioncylinder 14 and the drain tubes 13 a, 13 b and 15 are located as closeto the plasma luminescence point P1 as possible.

Here, the nozzle 7 is located outside the convergence region E2 and nearthe charged particle collection (receiving) cylinder 12 a. Furthermore,the charged particle collection (receiving) cylinder 12 b and the targetcollection cylinder 14 can be combined in one. That is, chargedparticles and droplet can be collected by a single retrieval cylinder.This is because by locating the nozzle 7 near the charged particlecollection (receiving) cylinder 12 a, the target collection cylinder 14facing the nozzle 7 can be located near the charged particle collection(receiving) cylinder 12 b. Thereby, it is possible to reduce collisionbetween charged particles, which are to be collected by the chargedparticle collection (receiving) cylinders 12 a and 12 b, and the nozzle7, and thus, it is possible to prevent the nozzle 7 from deteriorating.In addition, when the charged particle collection (receiving) cylinder12 b and the target collection cylinder 14 are combined in one, it ispossible to make the drain tube 13 b and 15 a single drain tube.Furthermore, it is preferable that the charged particle collection(receiving) cylinders 12 a and 12 b, the target collection cylinder 14and the drain tubes 13 a, 13 b and 15 are heated to a temperature of 300degrees Celsius in order to melt Sn accumulated in the charged particlecollection (receiving) cylinders 12 a and 12 b and the target collectioncylinder 14. Whereby, it is possible to liquidize the Sn accumulated inthe particle collection (receiving) cylinders 12 a and 12 b and targetcollection cylinder 14 a and easily eject the accumulated Sn to theexternal via the drain tubes 13 a, 13 b and 15 after liquidizing theaccumulated Sn.

Furthermore, in the first embodiment, as shown in FIG. 3, due to themagnetic field direction axis C2 and the ejection direction axis C1 ofthe droplet 17 being arranged crossways as having slopes while facingtoward approximately the same direction, when the droplet is charged,there is hardly any case where the droplet 17 passing through a magneticfield region E1 drifts from the ejection direction axis C1 of thedroplet 17 due to Lorentz force. As a result, it is possible to easilycontrol irradiation to the droplet 17 while an irradiation accuracy ofthe CO₂ pulse laser light with respect to the droplet 17 can beincreased.

Next, the angle (tilt angle) between the magnetic field direction axisC2 and the ejection direction axis C1 of the droplet 17 will bedescribed in detail. FIG. 4 is a schematic view for explaining a tiltangle of a nozzle. FIG. 5 is a schematic view for explaining a tilt ofthe nozzle. FIG. 6 is a schematic view for explaining Larmar radius.FIG. 7 is a schematic view showing a movement of a droplet inside amagnetic field. FIG. 8 is a schematic view for explaining a displacementof an emitted droplet inside the magnetic field. FIG. 9 is a schematicview for explaining a movement of a droplet inside the magnetic field.Firstly, as shown in FIG. 4, when a distance from the nozzle 7 to theplasma luminescence point P1 is L, a width of the convergence region E2is W, and the tilt angle is θ, the tilt angle θ is represented as thefollowing formula 1.

θ=arc sin(W/2L)   (formula 1)

Here, when a magnetic flux density is B, an energy of charged particle(ion) is E, a mass of the charged particle is m, a valence of ion is n,and an electric charge is q, as shown in FIG. 6, Larmar radius R_(L)that can be determined by a track TR is represented as the followingformula 2.

R _(L)=SQRT(2mE/nQB)   (formula 2)

Here, because the width W is 4R_(L), a minimum tilt angle θmin in a casewhen the nozzle 7 is located outside the convergence region E2 isdetermined as the following formula 3.

θmin=arc sin(2SQRT(2mE/nQBL))   (formula 3)

Accordingly, as shown in FIG. 4, the above-described tilt angle θ of thenozzle 7, namely the angle between the ejection direction angle C1 ofthe droplet 17 and the magnetic field direction axis C2 of the magneticfield region E1, can be set to be equal to or greater than the minimumtilt angle θmin.

For example, in a case of the magnetic flux density B=1[T], the energyE=0.6 [KeV], the valence of ion n=2.5, and the distance L=250 [mm], theθmin becomes 9.1 [deg]. That is, in this case, by making the tilt angleθ between the ejection direction axis C1 of the droplet 17 and themagnetic field direction axis C2 of the magnetic field region E1 set asgreater than 9.1 [deg], it is possible to prevent the charged particlesfrom colliding with the nozzle 7.

Here, if the droplet 17 is being charged in order to draw out aparticular droplet, or the like, the charged droplet 17 is to beinfluenced by Lorentz force. That is, the charged droplet 17 will beinfluenced by a vertical component Vv perpendicular to the magneticfield direction, from among the components in a self velocity direction.As an example, a case where the droplet 17 with mass m and valence qmoves in a uniform circular motion under the magnetic flux density Bwill be considered. In this case, as shown in FIG. 7, while the dropletmoves a distance 1 along a direction perpendicular to the magnetic fielddirection, the droplet 17 influenced by Lorentz force by as much as amovement h which is represented as the following formula 4.

h=( 1 ² qB)/(2mVv)   (formula 4)

Accordingly, as shown in FIG. 8, if the droplet 17 was ejected with thetilt angle θ with respect to the magnetic field direction axis C2, avertical component Vv and a horizontal component Vh of an initialvelocity V with respect to the magnetic field direction axis C2 isrepresented as the following formula 5, and the distance 1 that thedroplet 17 passes across the magnetic field while the droplet 17 movesthe distance L up to the plasma luminescence point P1 is represented asthe following formula 6. Therefore, as shown in FIG. 9, the movement hwhere the droplet 17 receives toward a direction perpendicular to themagnetic field direction axis C2 is represented as the following formula7.

Vv=V sin θ;

Vh=V cos θ  (formula 5)

1=L sin θ  (formula 6)

h=(L ² qB sin θ)/(2Vm)   (formula 7)

Here, when a maximum movement for enabling a position control to controlthe position of the CO₂ pulse laser light to the plasma luminescencepoint P1 is h′, a maximum angle θmax of the tilt angle θ is representedas the following formula 8.

θmax=arc sin(2Vmh′/L ² qB)   (formula 8)

That is, the tilt angle θ can be tilted as far as to the maximum angleθmax. According to the above description, it can be understood that thetilt angle θ should satisfy the condition θmin<θ<θmax.

Second Embodiment

Next, a second embodiment of the present invention will be described indetail. In the above-described first embodiment, the nozzle 7, thesupply tube 6, the charged particle collection (receiving) cylinders 12a and 12 b, the target collection cylinder 14, and the drain tubes 13 a,13 b and 15 are located in the space between the EUV collector mirror 8and the magnets 11 a and 11 b. On the other hand, in the secondembodiment, as shown in FIG. 10, a nozzle 27, a part of a supply tube26, a charged particle collection (receiving) cylinder 22 a, acollection cylinder 24 which collects (receives) both charged particlesand targets, and parts of drain tubes 23 a and 25 are located in bores11 c and 11 d, respectively. FIG. 10 is a vertical cross-sectional viewof an extreme ultraviolet light source apparatus according to a secondembodiment of the present invention when the extreme ultraviolet lightsource apparatus is cut at a cross-sectional face perpendicular to anoptical axis of an EUV light.

In the second embodiment, because the nozzle 27, the charged particlecollection (receiving) cylinder 22 a, the collection cylinder 24, and soon, are located in the bores 11 a and 11 d, it is possible to shorten aninterval between the magnets 11 a and 11 b. As a result, it is possibleto downsize the magnets 11 a and 11 b, and furthermore, it is possibleto further downsize the extreme ultraviolet light source apparatus as awhole.

Third Embodiment

Next, a third embodiment of the present invention will be described indetail. In the third embodiment, as shown FIGS. 11 and 12, an electricalfield generator is arranged around a nozzle head 37 a. Thereby, chancesof collision of charged particles against the nozzle can be reduced,whereby it is possible to effectively prevent deterioration of thenozzle. FIG. 11 is a cross-sectional view showing a structure around anozzle head in an extreme ultraviolet light source apparatus accordingto the third embodiment of the present invention. FIG. 12 is across-sectional view showing a structure around a nozzle head in theextreme ultraviolet light source apparatus according to the thirdembodiment of the present invention.

Normally, the charged particles converged by the magnetic field near theplasma luminescence point P1 is collected (received) by a chargedparticle collection (receiving) cylinder 32. However, in such a casewhere the charged particle has energy greater than expected, there is apossibility that the high energy charged particle flies out toward thenozzle head 37 a without converging within the magnetic field.Therefore, in the third embodiment, a charged particle collection(receiving) cylinder 38 covering the nozzle head 37 a has a negativepotential or a ground potential while the nozzle head 37 a has apositive potential applied to by a power supply 39. Thereby, chargedparticles with a positive potential bounce back against the nozzle head37 a by Coulomb force between the charged particles and an electricalfield being formed radially from the nozzle head 37 a. As a result, itis possible to prevent collision between the positive charged particlesand the nozzle head 37 a. Furthermore, it is also possible to preventthe nozzle head 37 a from being sputtered by decelerating the chargedparticles.

The charged particles (Sri⁺) drifted from the track toward the nozzlehead 37 a by Coulomb force are collected after adhering to an inner wallof the charged particle collection (receiving) cylinder 38. It ispreferable that a base of the nozzle head 37 a is covered with aninsulator 37 b in order to be insulated from peripheral structures.

In addition, as shown in FIGS. 13A and 13B, the Sn adhered to the innerwall of the charged particle collection (receiving) cylinder 38 can beheated by a thermal regulator 40 mounted around the charged particlecollection (receiving) cylinder 38 and a drain tube 41. Thereby, theadhered Sn liquidizes as a molten Sn 42 and is discharged from the draintube 41, whereby the Sn can be easily collected. FIG. 13A is a lateralview showing a structure around a nozzle head in an extreme ultravioletlight source apparatus according to a first alternate example of thethird embodiment. FIG. 13B is a cross-sectional view showing a structurearound the nozzle head in the extreme ultraviolet light source apparatusaccording to the first alternate example of the third embodiment. Themolten Sn 42 is supplied from a molten Sn reservoir 43 via a nozzle tube44.

Furthermore, as shown in FIGS. 14, 15A and 15B, it is possible toarrange an electrostatic grid 50 having an ejection aperture 50 a forejecting the droplet 17 around the nozzle head 37 a and apply a positivepotential to the electrostatic grid 50. By this arrangement, as in thecase where the nozzle head 37 a has the position potential directlyimpressed, an electrical field is formed toward the charged particlecollection (receiving) cylinder 38 from the electrostatic grid 50, andtherefore, the electrostatic grid 50 can deflect tracks of the chargedparticles from the track toward the nozzle head 37 a using Coulomb forcethat rebounds the charged particles. As a result, it is possible to letthe charged particles flying out toward the nozzle head 37 a adhere tothe inner wall of the charged particle collection (receiving) cylinder38. Furthermore, even if the track of the charged particle can not besufficiently deflected and the charged particle reaches theelectrostatic grid 50, it is possible to trap the charged particle bythe electrostatic grid 50. Moreover, by controlling a temperature of theelectrostatic grid 50, it is possible to liquidize depositions of thecharged particles (Sn⁺) having adhered to the electrostatic grid 50 soas to discharge and then collect the liquidized charged particles (Sn⁺)as the molten Sn 42. FIG. 14 is a vertical cross-sectional view showinga structure around a nozzle head in an extreme ultraviolet light sourceapparatus according to a second alternate example of the thirdembodiment. FIG. 15 is a lateral view showing a structure around thenozzle head in the extreme ultraviolet light source apparatus accordingto the second alternate example of the third embodiment. FIG. 15B is across-sectional view showing a structure around the nozzle head in theextreme ultraviolet light source apparatus according to the secondalternate example of the third embodiment. The molten Sn 42 is suppliedfrom the molten Sn reservoir 43 via the nozzle tube 44.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described indetail with reference to the accompanying drawings. FIG. 16 is avertical cross-sectional view of an extreme ultraviolet light sourceapparatus according to a fourth embodiment of the present invention whenthe extreme ultraviolet light source apparatus is cut at a faceincluding an optical axis of an EUV light. FIG. 17 is an illustrationshowing an example of a far field pattern transcribed on A-A surface inFIG. 16. In the following description, the far field pattern means apattern transcribed on A-A plane (cf. FIG. 16) as the EUV light Lbreflected by the EUV collector mirror 8 passes through a focus positionP2 in the EUV exposure apparatus 21.

Here, an obscuration region will be explained before explaining anextreme ultraviolet light source apparatus according to this particularembodiment. The obscuration region refers to a region E corresponding toan angular region in which EUV light Lb collected by the EUV collectormirror 4 is not used in the EUV exposure apparatus 11. That is, the EUVlight emitted from the plasma luminescence point P1 is focused on thefocus position P2 by the EUV collector mirror 4. In this explanation, athree-dimensional cubic region corresponding to the angular region inwhich the EUV light is not used in the exposure apparatus 11 at thefocus position P2 is defined as the obscuration region OB. Usually, theEUV light in the obscuration region OB is not used for exposure in theEUV exposure apparatus 11. Therefore, even if the EUV light in theobscuration region OB is not inputted to the exposure apparatus,exposure performance and throughput of the exposure apparatus will notbe influenced.

For this reason, in this particular embodiment, as will be described indetail later on, a head of the nozzle 7 (which may include the supplytube 6) is located inside the obscuration region OB. By this structure,it is possible to shorten an interval between the head of the nozzle 7and the plasma luminescence point P1, and therefore, it is possible toimprove a passing position stability of the droplet 17. As a result, itis possible to generate the EUV light Lb with stable intensity.

In addition, in the structure that the nozzle 7, and so forth, islocated inside the obscuration region OB, because only energy (lightintensity) in a region not used for exposure (transcribed pattern in theobscuration region OB) in the far field pattern (cf. FIG. 17) changes,such change will not influence the exposure in the EUV exposureapparatus 21.

Subsequently, the extreme ultraviolet light source apparatus 20according to this particular embodiment will be described in detail. Asshown in FIG. 16, the extreme ultraviolet light source apparatus 20 hasa structure similar to the extreme ultraviolet light source apparatus 10(show in FIG. 1, for instance) according to the first embodiment.However, as shown in FIGS. 16 and 17, in the extreme ultraviolet lightsource apparatus 20 according to this particular embodiment, at leastthe head of the nozzle 7 is located inside the obscuration region OB inthe vacuum chamber 1 while facing toward the plasma luminescence pointP1. Here, not only the head of the nozzle 7 but also a part or whole ofthe nozzle 7 and the supply tube 6 can be located inside the obscurationregion OB. Furthermore, the target collection cylinder 14 is located onan extension of a line C1 that passes through the head of the nozzle 7and the plasma luminescence point P1. In this arrangement, the head ofthe nozzle 7 and the target collection cylinder 14 are arranged in sucha way that a line passing through the head of the nozzle 7 and thetarget collection cylinder 14, that is, the ejection direction axis C1of the droplet 17, is included in a plane including an optical axis A1of the EUV light Lb and the magnetic field direction C2. Accordingly,the ejection direction axis C1 is tilted toward the optical axis A1 fromthe magnetic field direction C2.

More specifically, it is preferable that the head of the nozzle 7 islocated as close to the plasma luminescence point P1 as possible whilebeing outside the convergence region E2 (cf. FIG. 3). Thus, by arrangingthe head of the nozzle 7 outside the convergence region E2, as in theabove-described embodiments, it is possible to prevent the nozzle 7 frombeing damaged by the charged particles such as Sn⁺ ion, electron, and soon, having diffused from Sn plasma at the plasma luminescence point P1.Furthermore, by arranging the head of the nozzle 7 as close to theplasma luminescence point P1 as possible, it becomes easy to make thedroplet 17 ejected from the head of the nozzle 7 pass through the plasmaluminescence point P1 accurately, and to control timing at which thedroplet 17 passes through the plasma luminescence point P1. That is,according to this particular embodiment, it is possible to improve thepassing position stability of the droplet 17 without reducing the energy(light intensity) of the EUV light Lb that is valid for exposure in theEUV exposure apparatus 21. As a result, it is possible to generate theEUV light Lb with stable intensity.

Moreover, it is preferable to locate at least a part or whole of thetarget collection cylinder 14 inside the obscuration region OB. In thisarrangement, as with the nozzle 7, it is preferable that the targetcollection cylinder 14 is located as close to the plasma luminescencepoint P1 as possible while being outside the convergence region E2 (cf.FIG. 3). Thus, by arranging the target collection cylinder 14 outsidethe convergence region E2, it is possible to prevent the targetcollection cylinder 14 from being damaged by the charged particles fromthe plasma luminescence point P1. Furthermore, by arranging the targetcollection cylinder 14 as close to the plasma luminescence point P1 aspossible, it is possible to shorten an interval between the head of thenozzle 7 and the target collection cylinder 14, and therefore, it ispossible to have the target collection cylinder 14 steadily collectdebris such as residual droplets not having contributed to generation ofthe EUV light Lb, and so forth, for instance. As a result, it ispossible to generate the EUV light Lb with stable intensity. Inaddition, in this arrangement also, the energy (light intensity) of theEUV light Lb that is valid for exposure in the EUV exposure apparatus 21will not be reduced.

In this particular embodiment, the case where the head of the nozzle 7and the target collection cylinder 14 are located outside theconvergence region E2 while being inside the obscuration region OB hasbeen explained as an example. However, the present invention is notlimited to this case. It is also possible that the head of the nozzle 7and/or the target collection cylinder 14 are located as far from themagnetic field E2 as possible while being inside the obscuration regionOB. Thereby, even if the charged particle flies out from the magneticfield region E1, it is possible to steadily prevent the head of thenozzle 7 and/or the target collection cylinder 14 from being damaged.

Moreover, in this particular embodiment, as can be seen in the drawing,the case where the droplet 17 is ejected from the nozzle 7 located onthe upper side of the optical axis A1 (cf. FIG. 2, for instance) of theEUV light Lb toward the target collection cylinder 14 located on thelower side of the optical axis A1 while passing through the plasmaluminescence point P1 has been explaining as an example. However, thepresent invention is not limited to this arrangement, while it is alsopossible that the droplet 17 is ejected from the nozzle 7 located on thelower side of the optical axis A1 of the EUV light Lb toward the targetcollection cylinder 14 located on the upper side of the optical axis A1while passing through the plasma luminescence point P1.

Fifth Embodiment

Next, a fifth embodiment of the present invention will be described indetail with reference to the accompanying drawings. FIG. 18 is avertical cross-sectional view of an extreme ultraviolet light sourceapparatus according to the fifth embodiment of the present inventionwhen the extreme ultraviolet light source apparatus is cut at a faceincluding an optical axis of an EUV light. FIG. 19 is an illustrationshowing an example of a far field pattern transcribed on B-B surface inFIG. 18.

As shown in FIG. 18, an extreme ultraviolet light source apparatus 20Aaccording to this particular embodiment has a structure similar to theextreme ultraviolet light source apparatus 20 according to the fourthembodiment. However, as shown in FIGS. 18 and 19, in the extremeultraviolet light source apparatus 20A according to this particularembodiment, in the drawing, in the structure that the droplet 17 isejected from the nozzle 7 located on the lower side of the optical axisA1 (cf. FIG. 2, for instance) of the EUV light Lb toward the targetcollection cylinder 14 located on the upper side of the optical axis A1while passing through the plasma luminescence point P1, the nozzle 7and/or the supply tube 6 are mounted inside a through hole 8 b beingformed in the EUV collector mirror 8, and at least the head of thenozzle 7 projects from the reflective surface of the EUV collectormirror 8 toward the plasma luminescence point P1.

One aperture of the through hole 8 b is formed in a region correspondingto the obscuration region OB in the reflective surface of the EUVcollector mirror 8. On the other hand, the other aperture of the throughhole 8 b is formed on a back side of the EUV collector mirror 8 (asurface opposite to the reflective surface). That is, the through hole 8b penetrates the EUV collector mirror 8 from the back side (the surfaceopposite to the reflective surface) to the reflective surface of the EUVcollector mirror 8, for instance. However, it is not limited to sucharrangement. A through hole penetrating the EUV collector mirror 8 froma side surface to the reflective surface of the EUV collector mirror 8,or a notch formed at a rim of the reflective surface of the EUVcollector mirror 8 can also be applied.

Thus, by having the structure in that at least the head of the nozzle 7projects from the region opposite to the obscuration region OB in thereflective surface of the EUV collector mirror 8, it is possible toachieve the same effects as in the fourth embodiment. Additionally, inthis particular embodiment, because it is possible to arrange the EUVcollector mirror 8 and the plasma luminescence point P1 closer to eachother, it is possible to downsize the vacuum chamber 1 while it ispossible to increase a reflection solid angle with respect to the EUVlight Lb emitted from the plasma luminescence point P1, i.e. areflectance percentage with respect to the emitted EUV light Lb. As aresult, it is possible to make the extreme ultraviolet light sourceapparatus 20A high-power while downsizing the extreme ultraviolet lightsource apparatus 20A.

In addition, in this particular embodiment, as can be seen in thedrawing, the case where the droplet 17 is ejected from the nozzle 7located on the upper side of the optical axis A1 (cf. FIG. 2, forinstance) of the EUV light Lb toward the target collection cylinder 14located on the lower side of the optical axis A1 while passing throughthe plasma luminescence point P1 has been explained as an example.However, the present invention is not limited to this arrangement, it isalso possible that the droplet 17 is ejected from the nozzle 7 locatedon the lower side of the optical axis A1 of the EUV light Lb toward thetarget collection cylinder 14 located on the upper side of the opticalaxis A1 while passing through the plasma luminescence point P1. In thisarrangement, in place of the nozzle 7 and/or the supply tube 6, thetarget collection cylinder 14 and/or the drain tube 15 are mountedinside a through hole or a notch formed at the EUV collector mirror 8,while the target collection cylinder 14 projects from the reflectivesurface of the EUV collector mirror 8 toward the plasma luminescencepoint P1.

In the above-described first to fifth embodiments, charged particles aresimply made to adhere to the charged particle collection (receiving)cylinders 12 a and 12 b. However, it is also possible to further vacuumup the charged particles being adhered to the charged particlecollection (receiving) cylinders 12 a and 12 b via the drain tubes 13 aand 13 b.

Moreover, although neutral particles, and so forth, in the convergenceregion E2 are not ionized, it is possible to arrange an ionization meanssuch as an x-irradiator, an electron-irradiator, an ultravioletirradiator, a microwave irradiator, an EUV light irradiator, or thelike, in order to ionize such neutral particles, etc. By thisarrangement, it is possible to facilitate trapping of debris such asneutral particles, or the like.

According to each embodiment described above, because the nozzle islocated outside the convergence region in which charged particles areconverged in the magnetic field by Lorentz force while being inside thechamber provided for generating the extreme ultraviolet light, it ispossible to perform collection of debris and a resumption of residualtargets of which debris diffusion by the magnetical trap has beenprevented in closely place. As a result, it is possible to perform thecollection of debris and collection of residual targets using a simplestructure.

In addition, the above-mentioned embodiments and the alternate examplescan be arbitrarily combined with one another.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept of the invention as defined by the appended claims and theirequivalents.

1. An extreme ultraviolet light source apparatus generating an extremeultraviolet light from plasma generated by irradiating a target with alaser light, the extreme ultraviolet light source apparatus comprising:a magnetic field generator which generates a magnetic field regionaround a direction of the magnetic field passing through a plasma regionin which the plasma is to be generated and converges charged particlesincluding ion emitted from the plasma region toward the direction of themagnetic field; a first charged particle collector (receiver) mounted atboth sides of an axis of the magnetic field in the magnetic field regionin order to collect (receive) the charged particles converged by themagnetic field; a target supply unit supplying a target from a nozzlelocated outside a converging region in which the charged particles areto be converged inside the magnetic field region in an extremeultraviolet light generating chamber; and a target collector located ata position opposite to the nozzle, the target collector collecting aresidual target which does not contribute to generation of the plasma.2. The extreme ultraviolet light source apparatus according to claim 1,wherein The target collector and the first charged particle collector(receiver) located at the side of the target collector are a singlecollection portion.
 3. The extreme ultraviolet light source apparatusaccording to claim 1, wherein the axis of the magnetic field and an axisof supplying the target are tilted to make and angle between each other,and a tilt angle between the axis of the magnetic field and the axis ofsupplying the target is equal to or less than a maximum tilt angleallowing irradiation of the target with the laser light with respect tomovement of the target as occurred by a Lorentz force received while thetarget passes through the magnetic field.
 4. The extreme ultravioletlight source apparatus according to claim 1, wherein at least the nozzlehead is located within an obscuration region of the EUV light emittedfrom the plasma.
 5. The extreme ultraviolet light source apparatusaccording to claim 1, wherein at least a part of the target collector islocated within an obscuration region of the EUV light emitted from theplasma.
 6. The extreme ultraviolet light source apparatus according toclaim 1, wherein at least one or both of the target collector and thefirst charged particle collector (receiver) comprises: a liquescenceportion liquidizing a collected (received) material; and a drain portionejecting the material liquidized by the liquescence portion.
 7. Theextreme ultraviolet light source apparatus according to claim 1, whereinthe nozzle includes an electrical field generator generating anelectrical field in a nozzle head region, and a track of the chargedparticle is drifted from the nozzle head by the electrical fieldgenerated around the nozzle head region.
 8. The extreme ultravioletlight source apparatus according to claim 7, wherein the electricalfield generator includes an electrostatic grid covering the nozzle headregion except an aperture for supplying the target.
 9. The extremeultraviolet light source apparatus according to claim 7, furthercomprising: a second charged particle collector (receiver) collectingcharged particles of which track is drifted by the electrical fieldgenerator.
 10. The extreme ultraviolet light source apparatus accordingto claim 9, wherein the second charged particle collector (receiver)comprises: a liquescence portion liquidizing a collected (received)material, and a drain portion ejecting the material liquidized by theliquescence portion.
 11. The extreme ultraviolet light source apparatusaccording to claim 7, wherein at least the nozzle head is located insidean obscuration region of the EUV light emitted from the plasma.
 12. Theextreme ultraviolet light source apparatus according to claim 7, whereinat least a part of the target collector is located within an obscurationregion of the EUV light emitted from the plasma.